Bupropion hydrochloride is a well-known antidepressant. It is sold in the United States by Glaxo Wellcome Inc. as prompt release tablets under the tradename WELLBUTRIN.RTM. and sustained release tablets under the tradename, WELLBUTRIN SR.RTM..
Bupropion hydrochloride is known to be relatively unstable, such that tablets containing bupropion hydrochloride will degrade at an unacceptably high rate unless the tablets are made by a method or using ingredients which result in improved stability.
U.S. Pat. No. 5,358,970 discloses stabilization of bupropion hydrochloride by including in the tablets a stabilizer. The specific stabilizers disclosed are L-cysteine hydrochloride, glycine hydrochloride, ascorbic acid, malic acid, sodium metabisulfite, isoascorbic acid, citric acid, and L-cysteine hydrochloride. L-cysteine hydrochloride and glycerin hydrochloride are said to be most preferred. All of the examples in U.S. Pat. No. 5,358,970 use L-cysteine hydrochloride or glycine hydrochloride as the stabilizer, and, in each example, the process of manufacture includes the steps of dissolving the stabilizer in water and alcohol, using the solution to granulate the bupropion hydrochloride and other ingredients, and then drying the wet mass.
Such a process has the disadvantage of requiring the use of water and alcohol, and requiring the steps of preparing the solution, using the solution to granulate powder, and drying the wet granulated material.
The object of the present invention is to enable stabilization of compositions comprising bupropion hydrochloride by using a stabilizer that is effective when added in dry form, so as to eliminate the need to use water, alcohol or any other solvent, and thus also eliminate the steps of preparing a solution, using the solution to granulate powder, and drying.